Vmax head

Sam88

Sam88

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Joined
Oct 30, 2006
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34
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37
Location
Ontario Canada
Another forum member and I are planning on building a drag sled out of a 94 Vmax twin. Its a Hauck 700 Big Bore.

Whats the most compression that anyone has run here on pump gas (93 octane) without detonation? I believe factory is 130psi I was thinking 170 is the MOST.

What compression is any of the 2 stroke guys here running?

One problem is, you could run 170 but the timing isn't able to be changed manually........ I think...
 
140 is about max on pump gas. Of course timing and squish factor in too. I have a 1000 srx that has 170 psi 15:1 ratio and I run 112 octane.
 
Is it possible to change the timing by moving the magneto position?

Sorry i'm only familiar with 4 strokes.
 
Our '94 and '95 stock vm6's have 150,,they came from the factory with
a thin H/G...we run premium in them always...
 
You can get an offset timing key from aftermarket companies like Hauck to change the timing.
 
you can change timing by elongating a contact in the mag. i have a schematic of this directly from yamaha, just need to dig it out. its actually a grass drag manuel from yamaha for the 94-95 twins. i will dig it up and get back with you.
 
snowdad4 said:
you can change timing by elongating a contact in the mag. i have a schematic of this directly from yamaha, just need to dig it out. its actually a grass drag manuel from yamaha for the 94-95 twins. i will dig it up and get back with you.
Click to expand...


Please do, we don't want to have to buy an aftermarket ignition system. The only one i've seen that would be worthy is the MSD electronic, its 1000$ for that we might as well fuel inject it and run megasquirt and spark.
 
find your pulsor coil, elongate the mounting holes, 1.3mm = 1degree of timing advance. if you mess with the timing YOU MUST RUN quality fuel. on that sled a blend of 92 octane pump mixed 50/50 with 100 LL avation fuel would be adequate.
 
snowdad4 said:
find your pulsor coil, elongate the mounting holes, 1.3mm = 1degree of timing advance. if you mess with the timing YOU MUST RUN quality fuel. on that sled a blend of 92 octane pump mixed 50/50 with 100 LL avation fuel would be adequate.
Click to expand...

We're planning on running 100+ octane with a 50/50 blend of 94 Octane.

Is the pulsar coil in the same assembly as the stator?

We pulled the engine today and took the head off, its looking good, the cylinders don't need to be honed, we're going to do a full rebuild, shave the head, open up the ports. Its already trail ported, we're going to open them up a bit more.

We have the sled down to nothing now we're trying to find ways to lighten up the front end but its going to be hard without compromising strength.
 
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get on the yamaha on line parts finder for your year sled, look up the generator, you will find the coil. once you find it on your sled it will make sense as to elongating the mounting holes. you can only do so much, but i think 3 degrees advance was the most we went. some custom cut washers to hold the coil in place made the max. you dont necessarily have to go this far. try it in 1 degree increments
 
if memory serves correctly, no. dig down to the mag and it should all come in to view. seems as though the coil picked up impulse off the maf outer edge. its been awhile so if anyone else wants to pipe in, feel free.
 
I'm guessing its the little square thing on the outside part of the assembly with 1 screw on each side of it.

We ripped the sled down to nothing, its pretty much just a chassis with a skid and brake and front suspension. We need to start on the engine and lightening the chassis, we've discovered a bunch of brackets that can be removed and replaced with thinner, lighter pieces and some areas that can be drilled out.
 
So we figured out that we're going to aim for 170lbs of compression running on a 50/50 blend of C16 and 94 with a good amount of advanced timing which is hopefully no more then 3 degrees, if so then i'll have to fab up a new bracket to hold the pulsar coil. This is going to be done on a fully rebuilt 600 bottom end with a hauck 700 big bore top end, race ported, reed's, carbs bored to 40mm hooked up to mufflerless DG twin pipes.
Looking for 120mph+ in 1000ft if we get that then we'll be satisfied for a while, if not then...... Well lets say we have something planned.
 
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